The 16 years in which Ratko Mladic has roamed free in Serbia is not a long time in Balkan memory. It's no more than the blink of an eye. Besides, the arrest of Europe's most wanted war crimes suspect has as much to do with the present as the past. The chief prosecutor of the Yugoslav war crimes tribunal (ICTY), Serge Brammertz, was just about to deliver a damning verdict on Belgrade's reluctant pursuit of Mladic to the UN, a report which would almost certainly have doomed Serbia's bid to be declared a formal candidate for EU membership later this year. Serbia has already fallen years behind Croatia, which can reckon on becoming the 28th member in 2013. President Boris Tadic, who faces unrest on the streets and a challenge from a strengthening nationalist opposition, had to deliver – and deliver quickly. The EU, for its part, will now come under strong pressure to reciprocate. It is no exaggeration to say that the arrest of one man could open a new chapter in relations between his country and Europe.

Nothing about the stocky former general has ever been diminutive. He has, according to just two counts on the ICTY charge sheet, the blood of 17,000 victims on his hands – the massacre of 7,000 men and boys at Srebrenica in 1995 and the siege of Sarajevo, which claimed 10,000 lives. This was more than died during the German occupation. And yet the fact that he has evaded capture for so long speaks volumes about the raw memory of those terrible events. Consider the reaction yesterday of the Serbian Radical party, whose spokesman accused Serb police of treachery for arresting a Serb hero. According to one poll, 40% concur with that view, and 51% would not hand Mladic over to the tribunal. Mladic's insider knowledge of how the security services worked was surely not the only factor that kept him one step ahead of the game for 16 years. It was also the fact that he remained, to the people who began protesting in Belgrade last night, a hero worth protecting.

The cauldron of ethnic cleansing is still warm to the touch in this part of Europe, and it was only last month that Serbia agreed to hold face-to-face talks with Kosovo, whose independence it refuses to recognise. Belgrade also plays a major role in the calculations of the Bosnian Serbs, and their demands for a breakaway statelet from Bosnia-Herzegovina. If the Kosovans were allowed to break away from Serbia, why, they argue, are Bosnian Serbs to be denied the same right? The embers of this fire are still smouldering and could easily reignite. The trial of Mladic, and the painstaking unveiling of the evidence against him, will do nothing immediately to douse passions. Indeed they could fan them. The demonstrations organised by the Serbian Radical party will inevitably turn up the heat in the nine or 10 days that it will take for Mladic to be transferred to the international tribunal in the Hague. In that time, the courts and Tadic himself will both have to hold firm.

But in the long run, the state's unswerving determination to deliver Mladic to international justice is the strongest message any government in Belgrade could give to its neighbours that it intends to turn the page of history and start rebuilding the country and the region. Put to one side the carrots of EU membership. Mladic's deliverance to the Hague is the only conceivable route to establishing normal relations between all the beleaguered, and still impoverished, communities of the region. It is the only way of re-establishing Serbia's place in the Balkans, not as a pariah state but as a modern trading partner. It could also be a reminder to those manning fortress Europe of the cost of keeping the gates shut. France, Germany and the Netherlands, all suffering from enlargement fatigue, have been setting new conditions on Croatia's membership. Yesterday, Nicolas Sarkozy changed tack, acknowledging that it was impossible to tell Serbia now that the door was closed. The dinar has dropped.